what size are the stock apex seals in a 12a motor? I was always under the impression that they were 1 maybe 2mm. and thought the gsl-se has 3mm seals and tII's had 2mm's??????? can anyone straighten this out for me????

 

The apex seals are probably more on the order of 5 or so mm. The side seals could be 1 or 2mm, though.

 

???
WTF 5MM???


12a and pre 1985 13b's are 3mm steel
post 85 are 2mm steel

some really old 12a's and 10a's had 6mm carbons

 

thanks for the clarity. Always good to know. 85 and up are 2 piece as well correct?

 

till the 3rd gen went to 3
im not 100% on that tho

BTW i think all new mazda seals and replacements are 2 peice

 

FC had three piece.

 

thx

 

Guys guys guys....

The '67-73 engines all had 5mm or 6mm (sorry, I forget) carbon-aluminum one piece apex seals. Main reason why the early engines had such a poor reputation for wearing out quickly and poor low-RPM torque.

For '74 all rotaries went to a cast iron apex seal that was 3mm wide (for lightness, a 5mm iron seal would suck) and two-piece for better sealing at low RPM because its length could self-adjust. Gas sealing a square-edged area is difficult.

Therefore, all single-distributor 12As and all 13Bs had 3mm seals, up until...

In '86, Mazda went to 2mm wide seals that were three pieces, this time to help eliminate apex seal chatter and further improve sealing. ALL rotaries from '86 on up have 2mm seals. Including the FD. Including the various Cosmo engines. Including the RX-8, although the RX-8 uses a shorter, 2-piece seal.